Demonic EMpowerment for the Felguard says it is suppose to break all stuns, snares, and movement impairing effects, and make them immune to them. It does that for every single class cc in the game, except one. Demonic Empowerment does not break or make the Felguard immune to the Turn Evil.

It has been this way since 4.0 and not a single word about it has been said, and I can only imagine it is a bug if the spell breaks every other single cc from classes in game.